The Hum Is Probably Tinnitus, Norwegian Study Finds
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- NTNU researchers led by Professor Markus Drexl studied 28 people in Germany who reported hearing an unexplained hum, publishing the results in PLOS One.
- The study tested two main hypotheses — external low-frequency sounds that could be measured and inner-ear oto-acoustic emissions — and found neither matched most participants.
- Most participants showed no exceptional low-frequency hearing sensitivity; only 2 of the 28 had better-than-average hearing at certain low frequencies, undercutting the idea that sufferers simply have superhuman ears.
- The team concluded the most likely explanation for most cases is subjective low-frequency tinnitus, where the perceived sound originates within the auditory system despite feeling completely external to the listener.
- Drexl noted that hearing science has historically focused on higher frequencies, leaving the auditory system's handling of low-frequency sound and infrasound (below 20 Hz) poorly understood and limiting tools to investigate the phenomenon further.
- The Hum was first widely reported in Bristol, England in the mid-1970s and has since been documented across the US, Canada, Australia, New Zealand, South Africa and several European cities, affecting an estimated 2-4% of people worldwide.
Why it matters: For the estimated 2-4 percent of people worldwide who report The Hum, the finding reframes a decades-long mystery: instead of pointing to external culprits like industrial fans, traffic or wind turbines, the most likely cause is low-frequency tinnitus originating inside the auditory system — a conclusion the researchers note requires deeper study of how the ear processes low-frequency sound.
